The present invention relates in general to devices for stabilizing tissue and to methods for using such tissue-stabilizing devices, particularly cardiac tissue stabilizers. More particularly, the present invention relates to medical devices designed to stabilize the heart, for example, to retain the heart physically in an stabile position, during cardiac surgery. The apparatus of the present invention allows a surgeon to perform cardiac surgery on a warm beating heart, thus eliminating the need to place a patient on a cardiac bypass machine to stop the heart from beating. The methods and apparatus of the invention are particularly useful when performing coronary artery bypass grafting procedures such as coronary anastomosis.
There are many instances in which tissue needs stabilization. One common instance is in the case of broken bones. Broken bones need to be set and then held rigid and in a stabile position by a cast in order to heal properly. Sprained joints, such as sprained ankles, wrists, and fingers, also require tissue stabilization. In these cases, splints, tapes, and bandages are often used to maintain the joint in a relatively stabile position. Other instances include neck and spinal injuries.
In addition to these examples of external tissue stabilization, internal organs may also need to be stabilized for specific medical procedures. For example, the heart may need to be stabilized during cardiac procedures. One such procedures is coronary artery bypass graft surgery (CABG), which is the most commonly performed cardiac operation, accounting for over 80% of all cardiovascular surgery. Indeed, more than 400,000 CABG operations were performed in 1997 alone. The clinical spectrum of presenting problems resulting in consideration for CABG includes angina, unstable angina, congestive heart failure due to ischemia, myocardial infarction, survival of sudden cardiac death, and asymptomatic ischemia. In recent years, the profile of a typical CABG patient has expanded to include higher-risk patients, such as older patients and patients with more advanced stages of coronary artery disease, as well as patients for xe2x80x9cre-doxe2x80x9d operations who have already had at least one CABG operation. The effect of these changes is reflected in the higher morbidity and mortality associated with these higher-risk patients.
One of the risks involved in performing CABG is that the heart is stopped to provide a stabile operating platform. This is accomplished through the use of catheters, a heart-lung machine, and cardioplegia. After the procedure has been finished, the heart needs to be defibrillated. Risks involved in stopping the heart include damage from the catheters such as in the creation of thrombi and the possibility that the heart will not defibrillate.
In recent years, advances have been made so that the heart does not need to be stopped in order to perform CABG procedures, allowing CABG to be performed on a warm, beating heart. To do so, a relatively stabile operating platform needs to be maintained. Conventional apparatus developed to provide a stabile operating platform include devices which apply pressure against the heart and devices with a finger-shaped configuration which adhere to the heart through suction. To apply these devices to the heart, it takes both of the surgeons hands to position the devices on the heart. In addition, the devices do not establish secure contact with the epicardium of the heart and often need to be repositioned during the CABG procedure, which is time consuming and a nuisance.
In view of the foregoing, one of the objectives of the present invention is to provide methods and apparatus for stabilizing tissue which overcome the drawbacks of conventional techniques.
It is another object of the present invention to provide methods and apparatus for stabilizing a heart during cardiac procedures, particularly a warm, beating heart.
It is yet another object of the present invention to provide methods and apparatus for stabilizing tissue which may be applied at remote locations.
It is still another object of the present invention to provide methods and apparatus for stabilizing tissue with pneumatics.
These and other objects are achieved by the tissue stabilizers of the present invention and the method for their use which stabilize tissue through the use of pneumatics. In accordance with broad, functional aspects of the present invention, the tissue stabilizer of the invention includes a bladder which is substantially flexible when at ambient assure. However, when subject to negative pressure, such as through suction or vacuum, the bladder becomes substantially rigid. Because of these features, in use the tissue stabilizer may be positioned on tissue to be stabilized by, for example, wrapping the stabilizer around the tissue in the case of an arm, or contouring the stabilizer to the surface topography of the tissue in the case of a heart. When in a desired position, the rigidifying bladder may be subject to negative pressure, thereby rigidifying the tissue stabilizer. When rigid, the tissue stabilizer maintains the tissue in a stable position. The tissue stabilizer is particularly useful when configured for performing coronary artery bypass procedures (CABG) on a warm, beating heart.
In accordance with one aspect of the present invention, a tissue stabilizer includes a flexible rigidifying bladder and means for attaching the rigidifying bladder to tissue to be stabilized, such as straps with hook-and-eye fasteners. The rigidifying bladder includes a chamber, a port through which the chamber is evacuatable, and rigidifying structure disposed within the chamber. The rigidifying structure is configured to be substantially rigid when the chamber is evacuated. When the chamber is at ambient pressure, the rigidifying structure is substantially flexible to allow the stabilizer to be contoured to the tissue. The tissue stabilizer may include a valve for sealing the chamber when evacuated to maintain rigidity of the bladder.
The rigidifying structure may include opposing layers of mesh between which a plurality of movable beads are disposed. When the chamber is pneumatically evacuated, the rigidifying bladder collapses, thereby drawing the opposing layers of mesh together which, in turn, urges the beads together. The frictional forces between the beads and the mesh resist movement relative to each other, thereby providing rigidity. The rigidifying structure may include a plurality of walls which divide the inner chamber into a plurality of cells. The cells may be connected by air passages. The dividing walls prevent the migration of beads, thereby maintaining a substantially consistent distribution of beads and substantially consistent rigidity across the extent of the stabilizer.
The rigidifying bladder may also include a plurality of inner walls which separate the chamber into layers. The inner walls may includes air passages so that each of the layers is in pneumatic communication with each other. The rigidity of the rigidifying bladder is generally proportional to the number of layers. For example, in embodiments of the stabilizer configured to stabilize broken bones, the chamber may be divided into four or five layers, each of which includes a pair of opposing layers of mesh and a plurality of movable beads.
The tissue stabilizer of the present invention may be configured for many medical applications. For example, the tissue stabilizer may be configured as a portable neck brace for use by emergency medical teams for supporting and stabilizing an injured patient""s neck. The stabilizer may serve as a cast or a splint for stabilizing a broken bone that has been set. The tissue stabilizer may also be configured for athletic applications, such as protective gear or ankle support. The tissue stabilizer of the present invention is particularly useful in stabilizing the heart during cardiac procedures.
In this regard, an alternative embodiment of the tissue stabilizer of the present invention for cardiac applications includes a flexible first bladder for attaching the cardiac stabilizer to the heart and a flexible second bladder for rigidifying the stabilizer. Both bladders include an inner chamber and a port through which the chamber may be evacuated. The first bladder includes a plurality of openings which apply suction in response to suction applied at the port thereof. The second bladder includes rigidifying structure which rigidifies in response to suction applied at the port thereof. The cardiac stabilizer may include retaining structure which may be engaged with an external support for retaining the tissue stabilizer in a desired position when rigid. The cardiac stabilizer may also include a window for providing access to a surgical site.
In using the cardiac stabilizer to perform surgery, after providing access to the heart, the stabilizer is placed on the epicardium of the heart at a desired location, preferably with the window positioned over the surgical site. Suction is then applied at the port of the attaching bladder, thereby attaching the stabilizer to the heart. Suction then applied at the port of the rigidifying bladder, thereby rigidifying the cardiac stabilizer. A coronary artery bypass procedure may then be performed on the heart.
One of the advantages of the present invention is that the cardiac stabilizer may be contoured to the surface topography of the heart. This allows the attaching bladder to make secure contact with the heart, particularly when the heart has not been placed on a bypass machine (e.g., a heart-lung machine) but is warm and beating. The contouring allows the warm heart to be securely retained by the stabilizer, allowing the heart to be moved from the cardiac anatomical position to an anastomosis position. This is particularly advantageous when performing a bypass procedure on the circumflex branch of the left coronary artery. When the heart has been moved into an anastomosis position, the retaining structure of the cardiac stabilizer may be attached to external support structure to retain the heart in the anastomosis position.
One of the advantages of the invention is that the tissue stabilizer may be disengaged from the external support structure, de-rigidified, and detached from the tissue. This allows the stabilizer to be repositioned and then re-rigidified. In cardiac applications, such as on warm, beating hearts, the cardiac stabilizer may be disengaged from the external support, allowing the heart to be returned to the cardiac anatomical position if the heart should experience hemodynamic instability. When the heart regains stability, the heart may be repositioned in the anastomosis position and re-engaged with the external support.
Other objects, features, and advantages of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the present invention in the context of a cardiac tissue stabilizer but which are equally relevant to stabilizers for supporting other types of tissue.